1. Field of the Invention
The invention relates to vibration response and tuning of the center of mass or gravity of a centrifuge to provide high centripetal acceleration of a multi-welled container.
2. Description of the Related Art
Centrifuges are commonly used in laboratories to separate contents of a sample, remove bubbles in the sample, or otherwise modify the contents of a container via centrifugation. A centrifuge operates by rotating an object around a fixed axis and applying a force perpendicular to the axis. The centripetal acceleration of a centrifuge causes denser substances to separate out to the bottom of the container while lighter substances move to the top of the container. Increasing the gravitational force or g-force on the container will cause the contents of the container to more rapidly and completely separate or precipitate. A quicker and more effective centrifuge means that lab protocols can be completed more rapidly and means that fewer centrifuges are required since there is less need to run multiple centrifuges in parallel. Furthermore, some laboratory processes do not work if not enough g-force is applied to the samples.
Designing an effective, high g-force centrifuge can be a challenge, however. Centrifuges must be carefully balanced. When rotating a rotor around a fixed axis within the centrifuge at very high speeds, the centrifuge will commonly experience tilting or rotation if not properly balanced. Tilting of the centrifuge gives rise to gyroscopic forces that impart additional load on spindle bearings used in balancing the rotor, which wastes motor power and limits the g-forces obtainable. Thus, it is problematic to design a centrifuge that can use motor power effectively, has a low displacement during vibration, and has low vibration emissions to the foundation of the centrifuge, among other issues.
Centrifuging the contents of multi-welled containers, such as micro plates, is especially challenging due to the fact that there are many wells, only some of which may hold samples, including samples of different types. Small differences in mass of the load in the centrifuge can result in a large force imbalance when the rotor of the centrifuge is at a high speed. Thus, centrifuges that hold micro plates are more difficult to balance. As a result, they tend to be limited in the amount of centripetal acceleration that they can handle. Tabletop or laboratory benchtop microplate centrifuges can typically operate at 1000 g maximum, and most operate at less than that. They commonly have a maximum imbalance tolerance of 10 grams or less. Smaller centrifuges typically can only hold vials, and they only have tiny rotor. However, to centrifuge microplates, a bigger rotor is needed.
To provide a microplate centrifuge that can handle a larger centripetal acceleration, the centrifuge typically must be made much larger than standard tabletop centrifuges. These larger centrifuges are generally floor-mounted and are many times the size of the tabletop models. With these much larger centrifuges, the imbalance forces or oscillations/vibrations of the centrifuge can be overwhelmed due to the size and weight of the centrifuge. While these larger centrifuges can provide higher centripetal acceleration, they often are too large and unwieldy to use in laboratories. They have huge footprints, taking up valuable lab space. They are generally too big to integrate with other laboratory automation, such as robotic liquid handling stations that have robotic arms designed to load and unload multi-welled containers from centrifuges. Since the robotic arms cannot operate with these larger centrifuges, such loading/unloading must be performed manually, making the lab less efficient.
Centrifuges still have not overcome these various shortcomings. Currently, there are no multi-welled container centrifuges that solve the problems above, including permitting a high centripetal acceleration and imbalance tolerance while maintaining a small footprint and being robot accessible or able to integrate with laboratory automation equipment.